Three dimensional images, similar to depth maps, are obtained with a triangulation system using a television camera, and a deflectable laser beam diverged into a plane by a cylindrical lens. Complex objects are represented as structures joining parts called generalized cylinders. These primitives are formalized in a volume representation by an arbitrary cross section varying along a space curve axis. Several types of joint structures are discussed. Experimental results are shown for the description (building of internal computer models) of a handful of complex objects, beginning with laser range data from actual objects. Our programs have generated complete descriptions of rings, cones, and snake-like objects, all of which may be described by a single primitive. Complex objects, such as dolls, have been segmented into parts, most of which are well described by programs which implement generalized cylinder descriptions.